Antenna size can be reduced by loading the antenna with dielectric material. Because the wavelenght is shorter in the dielectric the size of the antenna can be made smaller for a certain electrical size. What happens with directivity and gain? Is the radiation efficiency changed?
What about...
Anyone has experience of radio controlled switches? I intend to design a circuit able to switch on/off 230V equipment remotely (mainly thinking of turning on the sauna without taking those 100 steps needed). Any good schematics on the web? This should work up to 100m free space.
What about the...
Suppose you place an antenna at x=-d in material with permittivity e1. At x=0 the permittivity changes to e2 while the space is homogenious in y- and z-direction. In material with permittivity (relative) e>1 the wavelenght is shorter than in free space causing the resonance of an fixed size...
If the radiation efficiency of a receiving antenna is poor or the antenna has to be loaded in order to get enough bandwidth, how does this affect the noise figure of the receiving system? As an example we can take an electrically small antenna which usually have narrow bandwidth. To increase...
Could anyone give me a hint on electrically small antennas for 433 MHz? The antenna shouldn't be larger than about 30mm in diameter and it will be placed close to a ground plane (1mm). I know that the antenna performance will be extremely poor but maybe some solutions are better than the others...
Has anyone an idea where I could find an air pressure sensor that could be connected to my home alarm (if the pressure changes it means that a door or a window is opened)?Instructions to build one?
